In the case of a tread pattern having grooves of circumferential orientation, it has been noted that for some conditions of use, breaks could appear at the bottom of the groove. This is the case, for example, during a manoeuvre of steering the tire passing over an obstacle or a relief object on the roadway, said relief object being inserted into a groove or alternatively upon mounting obstacles (for example, kerb) with or without steering forces exerted simultaneously on the tire. During this steering manoeuvre, the obstacle or the relief object tend to hinder said steering, and the result is an increase in stresses in the material constituting the tread in particular at the bottom of the grooves.
It is known, in order to avoid attack by various objects which enter the grooves, to arrange protuberances which are continuous or discontinuous in the direction of the groove close to the bottoms of the grooves in order to prevent the spread of said objects towards the inside of the tread (in particular as far as the reinforcement belt of the crown of the tire). During steering manoeuvres, these protuberances, which are of low height (less than 50% of the depth of the groove), are generally insufficient to prevent an obstacle from entering, at least in part, the groove at the exact moment of turning the wheel.
Another solution consists of very substantially increasing the height of these protuberances with the aim of limiting as much as possible, or even preventing, the insertion of an object into the groove during the steering manoeuvre. Document GB 903 389 discloses such a solution. Japanese document 2002/234313 discloses a tread pattern comprising in a groove a rib intended to reduce the wear of a tread, this rib being provided with a plurality of transverse extensions intended to bear against the walls of the ribs of the tread pattern.
These solutions, however, have some drawbacks, which the present invention attempts to overcome. Of these drawbacks, mention may be made of the risk of having cracks appear at the bottom of the grooves, between the reliefs or ribs and the facing walls of said grooves or the risk of having reliefs partially or fully torn away. Furthermore these reliefs or ribs are not completely effective in the case which is of concern here, namely the presence of an object in the groove hindering steering of the tire (that is to say, necessitating a greater steering force).